Evaluation of viscosity in inflammation and ferroptosis process based on a bithiophene-containing hemicyanine dye with diminished solvatochromic effect

To decrease solvatochromic effect and keep a strong selective fluorescence response to the change of viscosity, we have designed and synthesized a novel mitochondria-targetable hemicyanine fluorescence probe BT-In for viscosity detection during inflammation and ferroptosis process. By using high electron-rich bithiophene as a low polar electron donor, and the electron-withdrawing indolium group as electron acceptor as well as mitochondrial targeting group, BT-In shows high selectivity and rapid response for viscosity in vitro and high fluorescence-on signal enhancement at 614 nm with a large Stokes shift of 112 nm. Bioimaging experiments display that the probe has good mitochondrial-targeting ability (Pearson's correlation coefficient 0.99) and high-contrast imaging ability for detecting viscosity in living systems.